Volume 18, Issue 7

A biomechanical model of the brain is presented, using a finite-element formulation. Emphasis is given to the modeling of the soft-tissue deformations induced by the growth of tumors and its application to the registration of anatomical atlases, with images from patients presenting such pathologies. First, an estimate of the anatomy prior to the tumor growth is obtained through a simulated biomechanical contraction of the tumor region. Then a normal-to-normal atlas registration to this estimated pre-tumor anatomy is applied. Finally, the deformation from the tumor-growth model is applied to the resultant registered atlas, producing an atlas that has been deformed to fully register to the patient images. The process of tumor growth is simulated in a nonlinear optimization framework, which is driven by anatomical features such as boundaries of brain structures. The deformation of the surrounding tissue is estimated using a nonlinear elastic model of soft tissue under the boundary conditions imposed by the skull, ventricles, and the falx and tentorium. A preliminary two-dimensional (2-D) implementation is presented in this paper, and tested on both simulated and patient data. One of the long-term goals of this work is to use anatomical brain atlases to estimate the locations of important brain structures in the brain and to use these estimates in pre-surgical and radiosurgical planning systems.

本文提出了一种基于有限元公式的脑部生物力学模型。重点模拟了肿瘤生长引起的软组织变形，并将其应用于解剖图谱与患有此类病理患者的图像配准。首先，通过对肿瘤区域进行模拟生物力学收缩，获得肿瘤生长前的解剖估计；然后应用正常图谱与该估计的肿瘤前解剖进行配准；最后，将肿瘤生长模型的变形应用于配准后的图谱，生成完全配准至患者图像的变形图谱。肿瘤生长过程在非线性优化框架中模拟，并由脑结构边界等解剖特征驱动。在颅骨、脑室、大脑镰和小脑幕施加的边界条件下，使用软组织的非线性弹性模型估计周围组织的变形。本文展示了初步的二维实现，并在模拟数据和患者数据上进行了测试。本工作的长期目标之一是使用脑部解剖图谱估计大脑中重要脑结构的位置，并将这些估计用于术前和放射外科计划系统。

It is known that when a tissue is subjected to movements such as rotation, shearing, scaling, etc., changes in speckle patterns that result act as a noise source, often responsible for most of the displacement-estimate variance. From a modeling point of view, these changes can be thought of as resulting from two mechanisms: one is the motion of the speckles and the other, the alterations of their ...

已知当组织受到旋转、剪切、缩放等运动时，产生的散斑图案变化会作为噪声源，通常是位移估计方差的主要来源。从建模角度来看，这些变化可归因于两种机制：一是散斑的运动，二是其形状的改变。

Scale is an important issue in the automated detection of masses in mammograms, due to the range of possible sizes masses can have. In this work, it was examined if detection of masses can be done at a single scale, or whether it is more appropriate to use the output of the detection method at different scales in a multiscale scheme. Three different pixel-based mass-detection methods were used for...

尺度是乳腺X线摄影中肿块自动检测的一个重要问题，因为肿块可能具有各种尺寸。本研究探讨了是否可以在单一尺度下进行肿块检测，或者更适合在多尺度方案中使用不同尺度下的检测方法输出。使用了三种不同的基于像素的肿块检测方法...

A common problem in many biomedical imaging studies is that of finding a correspondence between two plane curves which aligns their shapes. A mathematical formulation and solutions to this problem is proposed in this paper. The formulation exhibits desirable properties. It allows for one-to-one as well as non-one-to-one correspondences, it consistently compares shape, even in nonrigid situations, ...

在许多生物医学成像研究中，一个常见的问题是找到两条平面曲线之间的对应关系，以对齐它们的形状。本文提出了该问题的数学表述和解决方案。该表述具有理想的特性。它允许一对一以及非一对一的对应关系，即使在非刚性情况下也能一致地比较形状。

A new imaging modality is introduced to image electrical conductivity of biological tissues via contactless measurements. This modality uses magnetic excitation to induce currents inside the body and measures the magnetic fields of the induced currents. In this study, the mathematical basis of the methodology is analyzed and numerical models are developed to simulate the imaging system. The induce...

介绍了一种新的成像模态，通过非接触测量对生物组织的电导率进行成像。该模态利用磁激励在体内感应电流，并测量感应电流产生的磁场。本研究分析了该方法的数学基础，并开发了数值模型来模拟成像系统。感应...

Abdominal organ segmentation is highly desirable but difficult, due to large differences between patients and to overlapping grey-scale values of the various tissue types. The first step in automating this process is to cluster together the pixels within each organ or tissue type. The authors propose to form images based on second-order statistical texture transforms (Haralick transforms) of a CT ...

腹部器官分割是非常理想的，但由于患者之间的巨大差异以及各种组织类型的灰度值重叠，因此难以实现。自动化此过程的第一步是将每个器官或组织类型内的像素聚类。作者提出基于CT图像的二阶统计纹理变换（Haralick变换）形成图像...

The authors present a method (DMESH) for nonrigid cyclic motion analysis using a series of velocity images covering the cycle acquired, for example, from phase-contrast magnetic resonance imaging. The method is based on fitting a dynamic finite-element mesh model to velocity samples of an extended region, at all time frames. The model offers a flexible tradeoff between accuracy and reproducibility...

作者提出了一种方法（DMESH）用于非刚性循环运动分析，该方法使用一系列覆盖整个周期的速度图像，例如通过相位对比磁共振成像获取。该方法基于将动态有限元网格模型拟合到扩展区域在所有时间帧的速度样本。该模型在准确性和可重复性之间提供了灵活的权衡...

Stereoscopy can be an effective method for obtaining three-dimensional (3-D) spatial information from two-dimensional (2-D) projection X-ray images, without the need for tomographic reconstruction. This much-needed information is missed in many X-ray diagnostic and interventional procedures, such as the treatment of vascular aneurysms. Fast C-arm X-ray systems can obtain multiple angle sequences o...

立体视觉是一种有效的从二维投影X射线图像获取三维空间信息的方法，无需断层重建。在许多X射线诊断和介入程序中，如血管动脉瘤的治疗，这种急需的信息被遗漏。快速C臂X射线系统可以获取多个角度序列...

A real-time cardiac magnetic resonance imaging (MRI) system has been implemented using digital signal processing (DSP) technology. The system enables real-time acquisition, processing, and display of ungated cardiac movies at moderate video rates of 20 images/s. A custom graphical user interface (GUI) provides interactive control of data acquisition parameters and image display functions. Images c...

已使用数字信号处理（DSP）技术实现了一个实时心脏磁共振成像（MRI）系统。该系统能够以20幅/秒的中等视频速率实时采集、处理和显示非门控的心脏电影。自定义图形用户界面（GUI）提供了对数据采集参数和图像显示功能的交互控制。图像...